1. Field of the Invention
The present invention relates to an output voltage control apparatus for performing feedback control for the drive of, for example, an AC(alternating-current) machine, an induction motor, etc. through an electric power converting device including a voltage PWM (pulse width modulation) inverter.
2. Description of the Related Art
The conventional voltage PWM inverter detects an output voltage, computes a deviation of the detected output voltage value from a voltage command value, and compensates (controls) the deviation using a proportional and integral (PI) controller, etc. The conventional compensating method is disclosed by, for example, Japanese Laid-open Patent Publications (Tokukaisho) No.61-94585 and No.63-234878.
This compensation method applies to both analog system and digital system. The analog system uses a linear IC (operational amplifier), etc., and the digital system uses a central processing unit (CPU) and a digital signal processor (DSP) capable of performing high-speed operations, and a high-resolution and quick-response A/D converter, etc. capable of converting the output of an output voltage detector into digital data so that control is performed in a software operation process.
However, since the analog system requires a linear IC, etc. for each process, the control apparatus becomes costly, and the control becomes complicated. On the other hand, the digital system requires expensive components such as a CPU, a DSP, etc.